The invention relates to a luminaire comprising:
a reflector body which has a reflecting coating on its concave reflection side, which coating has a diffuse reflection component and a specular reflection component, and
means for accommodating an electric lamp on the reflection side.
Such a luminaire is described in the non-prepublished European Patent Application 00 201 209.4 (PH-NL000190).
The use of a reflective coating on a reflector body is attractive, because the reflecting surface then has a much higher reflection coefficient and thus a lower absorption than a metal, for example, aluminum reflector body.
In the described luminaire, the coating has a relatively high specular reflection component along with a relatively low diffuse reflection component. In this way, the luminaire described combines the advantage of a low absorption of incident light with a considerably high level of specular reflection of incident light. Consequently, the luminaire can achieve a high efficiency, that is to say, a high quantity of irradiated light as a percentage of the light generated by an accommodated lamp, which is accompanied by a substantially high concentration of the irradiated light.
However, the described luminaire has the drawback that, as a result of the diffuse reflection component of the coating, an area of the reflection side of the reflector body does not radiate as much light in a direction determined by the position of this area with respect to the lamp as would have been the case with a reflector body with a specular reflection side. The light intensity of the beam of light generated by the luminaire may then be too low in said direction in order to provide a sufficient light intensity in said direction.
It is an object of the invention to provide a luminaire of the type described in the opening paragraph, which, in operation of an accommodated electric lamp, has a relatively high light intensity in a chosen direction.
According to the invention, this object is achieved in that the reflection side has an area with a metal reflecting surface.
The light incident on the area, generated by the accommodated lamp, is reflected by that area at least substantially in a specular manner. As a result, it is specifically reflected in the direction determined by this area. The section of the field to be illuminated in said direction then acquires a relatively high light intensity.
By applying the coating, the area can be screened off so that it is not covered by coating. It is also possible to remove coating from the area, for example before the coating has hardened.
However, in an embodiment which can be easily realized, the area has a metal sheet cover. This embodiment has various advantages. Not only can the entire reflection side of the reflector body be provided with the coating, without this having to be removed in part, but the reflector body can also be made from an optically low-value material such as plastic or cast aluminum. The reflection side does not need to have a high-value surface either, such as a polished or an eloxated surface. Only the metal sheet needs to be made of an optically high-value metal, generally used for, for example, reflectors, for example, high-polish aluminum or semi-high-polish aluminum.
The metal sheet may be secured to the reflector body by means of, for example, glue. Alternatively, it may be secured mechanically, for example with tongues on the sheet that protrude through apertures in the reflector body and are bent or twisted behind the reflector body.
The metal sheet can essentially fully follow the surface of the area which it covers. If the area has, for example, a facetted structure, the metal sheet itself has the same structure and almost completely engages the reflector body.
In a variant of this embodiment, the metal sheet cover is positioned at least partly remote from the area. This variant has the advantage that, with a reflector body of a given basic shape, a variety of reflectors can be realized so that the reflector body can be optimized for a selected purpose.
It is advantageous if the reflecting coating has a surface remote from the reflector body and comprises a light-transmissive binder in which light-reflecting particles are dispersed, the surface remote from the reflector body being substantially free from light-reflecting particles. The surface remote from the reflector body is then smooth and has a high level of specular reflection. Furthermore, the smooth surface prevents contamination by dust to a large extent.
It is advantageous for a high level of specular reflection if the coating comprises not more than 75% by volume of light-reflecting particles.
The coating may have a first layer comprising a light-transmissive binder in which light-reflecting particles are dispersed, and a second layer being substantially free from light-reflecting particles on a surface remote from the reflector body.
The light-reflecting particles may be surrounded by a pigment skin. In this way, a further increase of the specular reflection component is achieved, in particular if the particles and the pigment skin have different refractive indices.
It is advantageous if the light-reflecting particles are chosen from halophosphates, calcium pyrophosphate, strontium pyrophosphate and titanium dioxide.
The light-transmissive binder may comprise a silicon binder.
The luminaire may have a housing in which the reflector body is accommodated. The housing may be closed by means of a window pane which covers a light exit window of the reflector body.
The luminaire may be suitable for accommodating a halogen incandescent lamp, such as a tubular halogen incandescent lamp. The luminaire may alternatively be intended for use with a high-pressure discharge lamp, such as a high-pressure sodium discharge lamp, or a high-pressure metal halide discharge lamp, for example, with a quartz glass or a ceramic discharge vessel, such as, for example, an aluminum oxide discharge vessel.
The reflector body may be divided, for example in a plane, by the means to accommodate a lamp. Such a division may simplify exchanging of a lamp. The luminaire may be suitable for a range of applications, such as sports field floodlighting, tunnel lighting, site floodlighting, canopy lighting at petrol stations, etc.